The present application relates to power conversion methods, systems, and devices, and more particularly to nonresonant conversion architectures.
Note that the points discussed below may reflect the hindsight gained from the disclosed inventions, and are not necessarily admitted to be prior art.
Power conversion is one of the most important applications of power semiconductors, and plays an important role in many systems. Power conversion can be used to shift the voltage of a power supply to match the operating requirements of a particular load, or to permit use of a variable-voltage or variable current supply, or to compensate for the variation expected in an unreliable power source, or to permit a unit to be usable with a variety of power inputs, or to compensate for shift in “power factor” when an AC supply is connected to a reactive load. In many cases there are different terms for particular kinds of power conversion, e.g. a DC-to-AC converter is often referred to as an inverter, and some types of AC-to-AC converter are referred to as cycloconverters. Many kinds of motor drive can be thought of as a kind of power conversion: for example, a variable-frequency drive can be regarded as a species of power converter in which the frequency of an AC output is adjustable. In the present application the term “power conversion” will be used to refer generically to all of these types.
The present inventor has previously filed on a new class of power converter device operation and device, which provides a nearly universal power conversion architecture. In one version of this architecture, each input line is connected to the middle of one phase leg having two bidirectional switches, and the switches are operated so as to drive the terminals of a link reactance from one input or the other. A corresponding output switch array is used to transfer energy from the link reactance into two or more output terminals as desired, to construct the output waveform desired. Preferably the link reactance includes an inductor which is shunted by a capacitor. This provides a nearly universal hardware architecture, which is operated to implement a desired power-conversion function. This architecture is suitable for DC-AC, AC-AC, and AC-DC conversion. However, the present inventor now provides additional improvements, which are applicable to these as well as other topologies.
Many DC-DC, DC-AC, and AC-AC Buck-Boost converters are shown in the patent and academic literature. The classic Buck-Boost converter operates the inductor with continuous current, and the inductor may have an input and output winding to form a transfer for isolation and/or voltage/current translation, in which case it is referred to as a Flyback Converter. There are many examples of this basic converter, all of which are necessarily hard switched and therefore do not have the soft-switched attribute, which leads to reduced converter efficiency and higher costs.
In a chain of patent applications dating back to 2006, the present inventor has disclosed a revolutionary new power conversion architecture, known as the “UPC” (or “Universal Power Conversion”) architecture. Some of these applications include published US applications US2008/0013351 and US2008/0031019, both of which are hereby incorporated by reference. The present application describes further improvements which are particularly advantageous in connection with UPC architectures, and may also be applicable to other architectures.